Flex :: Make A Custom Component Or Extend The List Component For A 2D Top Down View MAP ?

I'm building a top view 2D map, that it's objects are stored on the server.The kind of objects are 10 and might be a photo, label, button, lists, mix of them or labels with tooltips.The component must request the "areas" that are missing on screen.An area is 1000x1000 px and is cached in flex.To move in the map, will be like in google maps (drag-and-drop).I should be able to have another list and move objects from one to another using drag-an-drop on objects. Ex.: I grab an objects from a list and I move it on this map, I release the mouse button and the item is placed there.Now the problem is: I build a custom component for this trying to emulate the item renderer for performance and recyclage, implement drag-and-drop on objects and request the areas that are missing?

or

I extend the List component from spark and I add some features as multiple kind of itemrenderers and use recycle on them. Of course it must be able to request the missing areas on the screen and cache it's data.Maybe create a custom layout is needed too.What I need is something that must be really fluid, so the lighter this component is, the better.

UPDATE: *There will be not any object over another.

*I will not use hitTest on bitmaps because all bitmaps are wrapped in another component,as they,for now are itemrenderers.

Anyway I already begin to do this using a class that extends the SkinnableDataContainer and a custom layout. As the layout is not like a grid, is sparse, random items at diferent points(x, y).How to get the localX and localY, relative to item renderer and not to the Spark List, from a DragEvent in Flex 4?